Down syndrome is caused by trisomy 21, the presence of three copies of chromosome 21. the extra copy usually results from nondisjunction during meiosis. in some cases, however, the extra copy results from a translocation of most of chromosome 21 onto chromosome 14. a person who has had such a translocation in his or her gamete-producing cells is a carrier of familial down syndrome. the carrier is normal because he or she still has two copies of all the essential genes on chromosome 21, despite the translocation. however, the same may not be true for the carrier’s offspring.

The scientific method is a series of steps followed by scientific investigators to answer specific questions about the natural world. it involves making observations, formulating a hypothesis, and conducting scientific experiments.the steps of the scientific method are •observation-the first step of the scientific method involves making an observation about something that interests you•question-once you've made your observation, you must formulate a question about what you have observed. •hypothesis-once you've made your observation, you must formulate a question about what you have observed. •experiment-once you've developed a hypothesis, you must design and conduct an experiment that will test it.•results-the results are where you report what happened in the experiment. •conclusion-the final step of the scientific method is developing a conclusion.i hope that this you : )

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